DTMB is the digital TV standard for mobile and fixed terminals used in the People's Republic of China, Hong Kong, and Macau. In DTMB systems, instead of a cyclic prefix, a PN sequence precedes each DTMB symbol acting as a guard interval and as pilots for the symbol. As specified by the DTMB standard, all of the PN sequences have the same generator polynomial, but their initial phase offsets are periodically varied. FIG. 1 illustrates initial phase offsets for the PN sequences for symbols in a DTMB frame where on the horizontal axis are the PN indices and on the vertical axis are the PN phase offsets for the given PN indices.
The PN sequence is used to aid estimating frequency offset and sampling frequency offset, and in channel estimation, the PN sequence is used to remove inter-symbol-interference (“ISI”). Generally speaking, the PN sequence needs to be estimated beforehand because the PN phase is critical for the synchronization process of the DTMB receiver. However, in receiving a DTMB signal, the PN phase is not known because the PN phase for the symbols varies by the respective offset (relative to PN0) and the PN phase of the received symbols need to be determined. Due to the large payload that can be carried by DTMB signals, in the decoding process, the calculation of the PN phase must be efficient in order to efficiently process the DTMB signals. Thus, it is desirable to have an efficient PN phase detector for use in DTMB receivers.